+ Extracts alpha from rgb24a images

git-svn-id: https://mlt.svn.sourceforge.net/svnroot/mlt/trunk/mlt@835 d19143bc-622f-0410-bfdd-b5b2a6649095

diff --git a/src/modules/avformat/filter_avcolour_space.c b/src/modules/avformat/filter_avcolour_space.c
index 50eb2ce46b613f17565db01dd866f4e89cd30288..53b6780c2c3321890a043763096112e1a10d11b4 100644 (file)
--- a/src/modules/avformat/filter_avcolour_space.c
+++ b/src/modules/avformat/filter_avcolour_space.c
@@ -87,12 +87,43 @@ static int filter_get_image( mlt_frame this, uint8_t **image, mlt_image_format *
                int size = avpicture_get_size( out_fmt, *width, *height );
                uint8_t *output = mlt_pool_alloc( size );
                convert_image( output, *image, out_fmt, in_fmt, *width, *height );
+
+               // Special case for alpha rgb input
+               if ( *format == mlt_image_rgb24a )
+               {
+                       register uint8_t *alpha = mlt_frame_get_alpha_mask( this );
+                       register int len = *width * *height;
+                       register uint8_t *bits = *image;
+                       register int n = ( len + 7 ) / 8;
+
+                       // TODO: Proper check for big endian systems
+                       #ifndef __DARWIN__
+                       bits += 3;
+                       #endif
+
+                       // Extract alpha mask from the image using Duff's Device
+                       switch( len % 8 )
+                       {
+                               case 0: do { *alpha ++ = *bits; bits += 4;
+                               case 7:          *alpha ++ = *bits; bits += 4;
+                               case 6:          *alpha ++ = *bits; bits += 4;
+                               case 5:          *alpha ++ = *bits; bits += 4;
+                               case 4:          *alpha ++ = *bits; bits += 4;
+                               case 3:          *alpha ++ = *bits; bits += 4;
+                               case 2:          *alpha ++ = *bits; bits += 4;
+                               case 1:          *alpha ++ = *bits; bits += 4;
+                                               }
+                                               while( --n );
+                       }
+               }
+
+               // Update the output
                *image = output;
                *format = output_format;
                mlt_properties_set_data( properties, "image", output, size, mlt_pool_release, NULL );
                mlt_properties_set_int( properties, "format", output_format );
 
-               // Special case for alpha rgb - merge the alpha mask when it exists
+               // Special case for alpha rgb output
                if ( *format == mlt_image_rgb24a )
                {
                        // Fetch the alpha